Researchers answer whether a low-fat or low-carb diet is more successful for weight loss

The long-raging debate over whether cutting carbs or cutting fat is a better way lose weight is a false dichotomy, according to new research published in the American Journal of Clinical Nutrition that found successfully shedding pounds is less about what someone eats and more about who they are.

In the last three decades, the fight against obesity has focused on the seemingly reasonable advice to eat less and exercise more, or to count and limit caloric intake to lose weight, but as time and climbing obesity rates show this strategy is not the panacea many people hoped it would be, Arne Astrup, professor and head of the Department of Nutrition, Exercise and Sports at the University of Copenhagen, told FoodNavigator-USA.

As a result, he explained, public health advocates and others began the long search for which foods caused the most damage and could be limited in order to win the battle of the bulge.

“When the obesity problem would not go away, it led to the fat reduction era with the replacement of a lot of fat with fiber, but also a lot of starch and carbohydrates, and in some instances more sugars, which did not solve the problem. In fact, the obesity rate when up,”​ he said. “This started a new trend, the Atkins Diet, and the major focus on restricting sugars and starchy foods,”​ which like the low-fat diet worked for some, but not everyone.

Head-to-head comparisons of the two diets showed them working equally well for some, and not well for others, “which didn’t make sense,”​ Astrup said.

“What we started to do was try to understand what happens really when you eat carbohydrates and when you eat fat and what the satiety signals that go to the brain while you are eating that normally make you stop eating so you don’t consume more calories than you need,” ​he said.

What they found in their “groundbreaking” ​study published July 5 in the American Journal of Clinical Nutrition was the fasting plasma glucose and fasting insulin in people are correlated with weight-loss and gain based on diets with different glycemic loads or different fiber and whole-grain content.

Your body, rather than your diet, might matter more for weight loss​

The team re-analyzed three randomized clinical trials conducted in eight European countries that looked at the impact on weight of eating a diet higher in protein, higher in fat, lower in carbohydrates and on the glycemic index, higher in carbohydrates and the glycemic index, higher in fiber and whole grains or lower in fiber in whole grains. Instead of simply looking at the impact of the diets on randomized people, though, the researchers considered the impact of the diets on people who prediabetic, diabetic or had normal glycemic control.

What the found was when the results were stratified by the person’s insulin sensitivity the weight loss and gain results were significantly different than when the different types of people were lumped together.

Specifically, they found pediabetic individuals were extremely susceptible to weight gain when consuming a high-glycemic load diet, but saw substantial weight loss when consuming a diet with a low glycemic load or a diet high in fiber and whole grains – even without restricting calories.

Likewise, diabetic participants lost more on a high-fat and low-carbohydrate diet than on a low-fat and high-carbohydrate diet. This is the opposite of individuals with normal glycemic levels, who lost more on a low-fat and high-carbohydrate diet.

What this means is that both the low-fat and no-carb diets work – just not for everyone, Astrup said.

An immediate marketing opportunity​

As a result, he says, food and beverage manufacturers – especially those in the weight management space – “need to stratify their customers into different groups and maybe you need to have products that are developed specifically for different types” ​because what is healthy for group A is unhealthy for group C and vice-versa.

The study’s results also show that personalized nutrition is not a concept of the future, but something that consumers and the manufacturers that cater to them, can access now.

“Starting today, you can have your blood tested for a glucose level and if you are feeling very sophisticated your fasting insulin and with these two simple and accessible tests you can actually see what is best for you,”​ he said. “This is not something we need to wait ten years to use clinically. This is something we can start using today, and there are no adverse effects because it is not a medication. What we are doing is actually removing from your diet what would be harmful to you.”​